Spinning of polyamides into a low humidity environment



United States Patent SPINNING OF POLYAMIDES INTO A LOW HUMIDITYENVIRONMENT Werner Miinch, Cesano Maderno (Milan), and LuigiNotarbartolo and Gaetauo Bruni, Milan, Italy, assignors to PerfogitSocieta per Azioni, Milan, Italy No Drawing. Application July 22, 1953,Serial No. 369,717

Claims priority, application Italy August 6, 1952 6 Claims. (CI. 18-54)This invention relates to an improved spinning process applicable to theproduction of spun goods from synthetic linear polymers.

In spinning such polymers it is very diflicult to obtain well woundthread packages, such as bobbins, especially when operating at highspeed, as it is common practice to operate. Actually it is observed thatif no special precautions are taken the thread bobbins are not regularlywound or at any rate the winding swells out in such a way that itbecomes difficult later to unwind the thread and that in so doingnumerous breakages occur. These phenomena are attributedto theabsorption of moisture on the part of the thread. It has been suggestedto avoid the trouble by extruding the polymer in an atmosphere of steam.However the use of steam is a complication and has drawbacks of its own.

According to the invention, the purpose of avoiding the aforementionedtroubles is achieved in a very simple and advantageous manner andperfectly wound yarn packages are obtained, by extruding the polymer inthe customary way, by winding up the resulting thread at a suitabletemperature in an atmosphere with a low relative humidity, preferablyless than 50%, and by leaving the wound thread in such atmosphere duringsome hours. After such treatment, not only is it possible to unwind thethread without ditliculty, but it is found-and this is unexpected andsurprising-that it may be unwound equally well even if it is left beforeunwinding for hours or even days in an atmosphere with such a relativehumidity as would have caused a bad winding of the yarn if the same hadbeen formed by direct extrusion in said atmosphere.

The advantages of the invention will be made clear by the followingcomparative example which has a character of illustration implying nolimitation and which refers to one particular polymer, and precisely toa polyamide obtained by polymerization of aminocaproic acid or ofcaprolactam. If such a polyamide is spun from the melt at a speed, forinstance, of 1000 meters per minute, forming a 15 denier yarn in anatmosphere at the temperature of 2023 C. and at the relative humidity of65-70%, the windings finally obtained uponbobbins are considerablyswollen, so much that the yarn is practically detached from its support.If it is attempted to unwind these bobbins at a speed, for instance, of200 meters per minute, they unwind badly with a considerable number ofyarn breaks.

If the same polyamide is spun at the same speed and with the same countand is wound on bobbins in an en- "Ice vironment at the same temperaturebut at a relative humidity of 45%, the resulting bobbins are excellentand quite compact. If these bobbins are left in said low humidityatmosphere for a period of time which may go from 2 to 36 hours, butwhich is preferably comprised between 18 and 26 hours, and are laterbrought into an environment having the same temperature and a relativehumidity of -70% and are left there for some hours or even for .one ortwo days or even more, they can be unwound in this latter environment atspeeds even higher than 200 meters per minute without any difliculty andwithout any breakages occurring. The bobbins, after they have been woundand conditioned in the low humidity environment, swell but very littleif brought into a normal or relatively high humidity environment, andeven after they have remained therein a sufiiciently long time, contraryto what was to be foreseen.

What we claim is:

l. A process for the spinning of synthetic linear polyamides, comprisingthe steps of forming polyamide filaments by extruding a molten polyamidethrough a spinneret into an environment, maintaining in said environmenta relative humidity not higher than 50%, winding the extruded filamentsonto packages in the said environment, and conditioning said filamentpackages by keeping them in an environment having a relative humiditynot substantially higher than 50% for a period of time comprised ofbetween 2 and 36 hours.

2. A process according to claim 1, wherein the filament packages areconditioned by keeping them in an environment having a relative humiditynot higher than 50% for a period of time comprised between 18 and 36hours.

3. A process according to claim 1, comprising the additional step oftransferring the filament packages into an environment having a relativehumidity substantially higher than 50% and subsequently unwinding saidpackages therein.

4. A process according to claim 1, wherein the filaments are Wound ontopackages at a liner speed not substantially lower than 1000 meters perminute.

5. A process according to claim 1, wherein the environments having arelative humidity not substantially higher than 50% have a temperaturenot substantially lower than 20 C.

6. A process according to claim 1, wherein the polyamide, is thatobtained by polymerization of caprolactam.

References Cited in the file of this patent UNITED STATES PATENTS2,157,117 Miles May 9, 1939 OTHER REFERENCES Nylon Technology(Indefurth), published by Me- Graw-Hill (New York); pages 51, 196, 228relied on. (Copy in Scientific Library.)

Customer Service, Nylon, published by E. I. Du Pont; pp. 3-701 and3-8.01 relied on. (Copy in Scientific Library and in Div. 43.)

The Textile Manufacturer (British), April, 1939; p. 143 relied on. (Copyin Scientific Library and in 281N.) 7Ser; No. 307,983, Schlack (A. P.0.), published April 2 1 34.

1. A PROCESS FOR SPINNING OF SYNTHETIC LINEAR POLYAMIDES, COMPRISING THESTEPS OF FORMING POLYAMIDE FILAMENTS BY EXTRUDING A MOLTEN POLYAMIDETHROUGH A SPINNERET INTO AN ENVIRONMENT, MAINTAINING IN SAID ENVIRONMENTA RELATIVE HUMIDITY NOT HIGHER THAN 50%, WINDING THE EXTRUDED FILAMENTSONTO PACKAGES IN THE SAID ENVIRONMENT, AND CONDITIONING SAID FILAMENTPACKAGES BY KEEPING THEM IN AN ENVIRONMENT HAVING A RELATIVE HUMIDITYNOT SUBSTANTIALLY HIGHER THAN 50% FOR A PERIOD OF TIME COMPRISED OFBETWEEN 2 AND 36 HOURS.